March 15, 2009
Sea temperature: 0.589 °C
Air temperature: 1.5 °C
The surface mapping project continued through the night and into the early evening today as the ship followed a grid pattern around the iceberg. This pattern is referred to as “mowing the lawn”: the ship travels forward a given distance (in this case, 10 nautical miles), then turns ninety degrees to move over some distance (0.5nm), then turns another ninety degrees to drive back in the opposite direction for 10 nautical miles. Two such grids were completed around the iceberg.
As the ship made each turn for the grid, an XBT (expendable bathythermograph) sensor was released to measure temperature as a function of depth down to 1830m. XBTs are dropped over the side and are connected to the ship via a thin copper wire for data communications. But when the sensor reaches the end of the wire, it breaks off and the sensor itself is not recovered.
Scientists monitored the incoming data in the dry lab where video screens continuously display weather, ocean parameters, ship’s position, graphs from deployed instruments, and views from cameras throughout the ship. This area has been abuzz throughout the day as the principal investigators have been reviewing graphs and contour plots and discussing what the data might mean. Each research team has been taking notes to decide where they want to deploy their instruments based on the information from the surface mapping.
Just after dinner Alana Sherman, Ken Smith and Paul McGill successfully tested a Lagrangian sediment trap off the starboard A-frame, confirming that the sensor responds to remote acoustic commands in the water. As a final test early tomorrow morning, the LST will be released close to another, smaller iceberg that is in the area.
—Debbie Nail Meyer